Power supplies are used virtually in every electronic device primarily for converting alternate current (AC) or direct current (DC) electrical input that may vary in voltage due to power line conditions and load factors, into a constant direct current (DC) output voltage to power the internal circuitry of the electronic device.
Power supplies designed to convert a fluctuating input voltage to a constant, lower, output voltage can be realized by a linear converter. However, such linear power supplies are characterized by poor efficiency. If a linear power supply is used for delivering larger output current or power, the efficiency becomes detrimentally prominent.
A switched mode power supply (SMPS) is often used when a greater efficiency is desired. However, SMPSs use switching mechanism internally using switches and such internal switching is known to cause electromagnetic emission (or EMC noise). The SMPS typically includes an asynchronous converter that may also include one or more diodes. Reverse recovery characteristics of a diode is typically a cause of the production of the EMC noise.
To reduce the EMC noise, typically, an input filter is used. For certain types of applications, such as electronic systems used in automobiles, there may be regulatory requirements to keep the EMC noise below a preset threshold. The input filter is designed to keep the EMC noise below this threshold. In addition, the diode may also need to have superior reverse recovery characteristics that may need bigger space on a silicon wafer. Reducing the size of the input filter and possibly also the size of the diode may reduce the overall size and cost of a power supply.